Origins of transverse voltages generated by applied thermal gradients and applied electric fields in ferrimagnetic-insulator/heavy-metal bilayers

TL;DR

This paper investigates the origins of transverse voltages in ferrimagnetic-insulator/heavy-metal bilayers driven by thermal gradients and electric fields, revealing different mechanisms in W and Pt interfaces, with implications for spin current detection.

Contribution

It compares thermal and electrical transverse voltages in ferrimagnetic bilayers, identifying a common spin-current detection mechanism in W and a proximity-induced magnetic effect in Pt.

Findings

Thermal and electrical effects in Tm3Fe5O12/W are explained by spin Hall magnetoresistance.

In Tm3Fe5O12/Pt, the ratio of electrical to thermal signals suggests additional magnetic effects.

Proximity-induced magnetism at the Pt interface influences transverse voltage behavior.

Abstract

We compare thermal-gradient-driven transverse voltages in ferrimagnetic-insulator/heavy-metal bilayers (Tm3Fe5O12/W and Tm3Fe5O12/Pt) to corresponding electrically-driven transverse resistances at and above room temperature. We find for Tm3Fe5O12/W that the thermal and electrical effects can be explained by a common spin-current detection mechanism, the physics underlying spin Hall magnetoresistance (SMR). However, for Tm3Fe5O12/Pt the ratio of the electrically-driven transverse voltages (planar Hall signal/anomalous Hall signal) is much larger than the ratio of corresponding thermal-gradient signals, a result which is very different from expectations for a SMR-based mechanism alone. We ascribe this difference to a proximity-induced magnetic layer at the Tm3Fe5O12/Pt interface.